Electronic devices such as smartphones and tablet personal computers are extensively used because they are easy to use and easy to carry. Such an electronic device has a socket (e.g. earphone jack) to which an accessory can be connected.
The electronic device may use an accessory connected to the socket as an antenna. For example, when the earphone plug of an earphone is inserted into the earphone jack of the electronic device, the ground terminal of the earphone may be connected to the communication circuit of the electronic device. At this time, the ground line of the earphone may serve as an antenna. The electronic device may receive a Digital Multimedia Broadcasting (DMB) signal and/or an FM radio signal through the ground line of the earphone.
Meanwhile, the electronic device may include a codec circuit to send and receive an audio signal to and from the earphone. To increase the performance of the earphone (e.g. sound quality), the ground of the earphone may be connected to the ground of the codec circuit in the electronic device.
The electronic device may have a socket (e.g. earphone jack) to which an earphone (e.g. 3 or 4 pole earphone) can be connected or inserted. The electronic device may use the ground terminal of the socket for receiving a radio signal or for extending the ground of the earphone. As the ground terminal of the socket is connected with the ground of the communication circuit and codec circuit, a line may be used in common in the electronic device.
However, the width of the commonly used line should become large to enhance audio performance of the earphone (e.g. low crosstalk); and the width of the commonly used line should become small to enhance radio performance (e.g. impedance matching). Hence, it may be difficult for the electronic device to achieve audio performance and radio performance at the same time. In addition, when the commonly used line becomes long and the socket is placed at the lower end of the electronic device, it may fail to mount a specific component (e.g. inductor), which is to be located at the start point where the path leading to the communication circuit and the path leading to the codec circuit are separated, close to the socket owing to the lack of mounting space. In this case, the electronic device may fail to achieve audio performance and radio performance at the same time.